Aquatic sample analysis system

ABSTRACT

According to one aspect, the invention relates to an aquatic sample analysis system adapted for in situ use. The system includes an incubation chamber having an optically clear portion and forming an opening for receiving a fluidic sample and apparatus for sealing the opening. The system also includes a sensor for sensing at least one parameter associated with the sample inside the chamber, a control module in communication with the sensor, and a power source.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation patent application of U.S. patentapplication Ser. No. 13/476,531 filed on May 21, 2012 and claimspriority to and the benefit of U.S. Provisional Patent Application No.61/488,454, filed on May 20, 2011, the disclosure of which is herebyincorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was supported by the United States Government underNational Science Foundation Grant OCE1155438. The Government has certainrights in the invention.

FIELD OF THE INVENTION

The present invention relates generally to in situ systems for analyzingparameters of interest in aquatic environments and, more specifically,to systems having multiple incubation chambers for providing comparativeenvironmental conditions.

BACKGROUND OF THE INVENTION

The rates of photosynthesis and respiration define the role of lakes andoceans in the global carbon cycle: if photosynthesis exceeds respirationthen the water is a sink for CO₂, while if respiration exceedsphotosynthesis then it is a source of CO₂. Due to the relative ease ofincubation-based ¹⁴C primary production methods, the rate ofphotosynthesis has been measured many hundreds of thousands of times.Oceanographers and limnologists achieved a global view of photosynthesisrates by the late 1960s and the global database of ¹⁴C primaryproduction data continues to grow. This information has provided thebiological basis for potent satellite- and model-based analyses of oceanbiogeochemistry. In contrast, the rate of respiration has only beenmeasured about 2000 times and, thus, there is no global-levelunderstanding of aquatic respiration rates; this is a profound gap inour knowledge. In the ocean, the paucity of respiration rate data hasfueled an intense debate over whether the ocean is a net source or sinkof CO₂ on a global scale. Furthermore, there is very littleincubation-based respiration data to assess regional scale CO₂ balances,even within the coastal waters of the United States. Given theimportance of understanding CO₂ balance from both scientific andgeopolitical standpoints, the demand for respiration rate data willskyrocket in the next few years.

One of the primary reasons that the study of aquatic respiration hasfallen so far behind the study of photosynthesis is that respirationrates are difficult to measure. Heterotrophic bacteria play an importantrole in attenuating the flux of particulate organic carbon (POC) fluxthrough the twilight zone (i.e. shallow but dark waters); along withzooplankton, heterotrophic bacteria contribute to both particledisaggregation and attendant organic carbon respiration. The rates ofheterotrophic bacterial processes in the twilight zone are substantiallyslower than in the euphotic zone, and accurately measuring these ratesin the twilight zone presents numerous technical challenges. Manycurrent technologies for measuring photosynthesis or respiration involveremoving samples from their environment for incubation. A widely-appliedtactic is to bring twilight zone water samples to the surface and applyscaled up versions of incubation-based methods originally designed foruse in the euphotic zone; these methods are applied at atmosphericpressure and the effects of depressurization are assumed to benegligible. This has been done for measuring rates of tritiatedthymidine incorporation by heterotrophic bacteria. The thymidineincorporation rates can be compared to rates of bacterial carbon demand(BCD) and, although this rate conversion imparts large uncertainties,comparisons can be made between BCD, zooplankton carbon demand, and theloss of sinking POC flux. These results showed, both in North Pacificsubtropical gyre and the subarctic North Pacific, that twilight zone BCDgreatly exceeded the loss of POC, suggesting either: 1) that BCD wasoverestimated; 2) that POC flux attenuation was underestimated; or 3)that there were additional, large sources of organic carbon to thetwilight zone. Therefore, the rates of BCD should be better constrained.For example, enzymatic POC hydrolysis rates determined during testingcan add some additional bounds to the BCD dataset. However, furtherbounds are still needed.

Another surface method is to incubate seawater (light and dark) andmeasure the decrease in oxygen concentrations using the Winklertitration method, as is known in the art. The Winkler titration can bemessy, time consuming, and error prone and, as such, a major impedimentto the study of respiration at sea. Alternative methods have beenattempted, such as measuring oxygen with electrodes or tracking anincrease of CO₂, but these have not shown the reliability andsensitivity of the Winkler titration. Unlike photosynthesis, respirationis not confined to the sunlit waters of the ocean's surface. This isbecause organic particles from photosynthetic organisms sink from thesurface waters to the mesopelagic, where most of them are ultimatelyrespired. Since the Winkler titration is a wet chemical method, oxygenmeasurements of mesopelagic waters must be conducted on the deck ofship. This again introduces biases caused by depressurization of themicrobes responsible for respiration. Some studies that have addressedthe impact of pressure on microbial respiration suggest that thedepressurization biases may be quite large, even at relatively shallowdepths (e.g., 100s of meters).

Radioisotope methods can provide simple yet sensitive measurements;however, these methods are not generally available for measuringrespiration rates. One method is performed partially in situ. Thisapproach requires that the device sample and filter the incubation, andthat these filters be retrieved using a research vessel in order toquantify the desired process (e.g., to measure photosynthesis andrespiration). However, this method (and other radioisostope systems)have the disadvantage of being subject to regulatory constraintsassociated with the use of radioactive substances in the ocean.

Photosynthesis and respiration are arguably the defining parameters ofcarbon cycling in aquatic ecosystems (freshwater and saltwater), and arealso primary components of oxygen demand measurements (i.e., biologicaloxygen demand (“BOD”)) in the water quality community. Almost everymunicipality makes BOD measurements as part of their wastewatermanagement operations. The ability to easily make such measurements isalso of interest in the oceanographic community and plays a key role inthe Ocean Observatories Initiative.

Accordingly, there exists a need in the art for a reliable,cost-effective, in situ system for analyzing aquatic parameters ofinterest, such as determining respiration rates.

SUMMARY OF THE INVENTION

The present invention is directed toward novel systems and methods foranalyzing aquatic parameters in situ, such as through the use of aPhotosynthesis Respiration and Carbon Balance Yielding Sensor(“PHORCYS”). The PHORCYS may use an oxygen optode, for aquaticrespirometry. The PHORCYS allows incubations under in situ conditions,which more faithfully mimics the “real world” conditions. This is amajor advance over existing approaches, most of which are one-offlab-based systems and which suffer from changes in temperature, lightand pressure associated with removal of water from the in situconditions, as described above. The PHORCYS system does not requirechemicals of any kind, nor does it produce a sample that must becollected. The system can produce data continuously, without the needfor recovery aboard ship or additional sample processing.

According to one aspect, the invention relates to an aquatic sampleanalysis system adapted for in situ use. The system includes anincubation chamber having an optically clear portion and forming anopening for receiving a fluidic sample and a seal for sealing theopening. The system also includes a sensor for sensing at least oneparameter associated with the sample inside the chamber, a controlmodule in communication with the sensor, and a power source.

In accordance with one embodiment of the above aspect, the chamberincludes a tube with at least one open end covered by the seal. At leastone open end may be sealable with a spring-loaded cap, which may bebiased toward a sealing position. In another embodiment, the at leastone open end is sealable with a ball valve, and/or the at least one openend is sealable with a hinged cap. In some embodiments the parameter maybe oxygen concentration, nitrate concentration, carbon dioxideconcentration, or pH. The sensor may be an oxygen optode, a UV-basednitrate detector, a colorimetric carbon dioxide sensor, and/or acolorimetric pH sensor. The control module may be adapted to providepower to the sensor and receive sensor output, and may also store thesensor output and/or transmit the sensor output.

In other embodiments, the system includes an optically opaque incubationchamber. The opaque chamber may include a sensor for sensing at leastone parameter associated with a sample inside the opaque chamber. Theparameter may be oxygen concentration, nitrate concentration, carbondioxide concentration, or pH. The control module may be adapted tocompare respective outputs of the clear chamber sensor and the opaquechamber sensor, and may be adapted to determine instantaneous oxygenconcentration, gross respiration rate, gross primary production rate,and/or net primary production rate.

In another aspect, the invention relates to a method of analyzing anaquatic parameter in situ. The method includes the steps of deploying anaquatic sample analysis system to a location and depth of interest andobtaining a fluidic sample at the location and depth of interest. Themethod also includes measuring a parameter of interest associated withthe sample over an incubation period, determining a rate-of-change ofthe parameter of interest, and calculating at least one of a grossrespiration rate, a gross primary production rate and a net primaryproduction rate based at least in part thereon.

In accordance with one embodiment of the foregoing aspect, the aquaticsample analysis system includes an incubation chamber including anoptically clear portion and an optically opaque incubation chamber. Thefluidic sample may be disposed in each incubation chamber. In someembodiments, the parameter of interest is oxygen concentration. Themethod may also include releasing a fluidic sample and obtaining a newfluidic sample, and may further include transmitting data based at leastin part on the parameter of interest from the system to a remotelocation.

In still other embodiments, the calculating step includes calculatinggross respiration rate based at least in part on rate-of-change ofoxygen concentration in the optically opaque incubation chamber,calculating net primary production rate based at least in part onrate-of-change of oxygen concentration in the optically clear incubationchamber, and determining gross primary production rate based thereon.The incubation period may occur at least partially during daylight.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the present invention, as well as theinvention itself, can be more fully understood from the followingdescription of the various embodiments, when read together with theaccompanying drawings, in which:

FIG. 1 is a schematic, front perspective view of an aquatic samplecollection system, in accordance with one embodiment of the invention;

FIG. 2 is a schematic, front perspective view of an incubation chamberusable with the aquatic sample collection system of FIG. 1, inaccordance with another embodiment of the invention;

FIG. 3A is a schematic front view of an oxygen optode for use with anincubation chamber, in accordance with one embodiment of the invention;

FIG. 3B is a schematic front view of an incubation chamber usable withthe oxygen optode of FIG. 3A, in accordance with one embodiment of theinvention;

FIG. 4 is a graph of oxygen concentrations over time based on datacollected with the aquatic sample collection system of FIG. 1; and

FIG. 5 is a graph of oxygen concentrations over time measured withdifferent incubation chambers using an onboard method.

DETAILED DESCRIPTION OF THE INVENTION

The invention may be better understood by reference to the followingdetailed description, taken in conjunction with the figures. Variousembodiments of the invention relate to a system for analyzing aquaticparameters in both freshwater and saltwater. Other configurations andvariants will be apparent to those skilled in the art from the teachingsherein and are considered to be within the scope of the invention.

The PHORCYS system is in various embodiments an expandable and versatilefamily of instruments containing one or more incubation chambers and aunique combination of sample collection systems and sensors that areused to measure photosynthesis and respiration in aquatic and marinesystems under in situ conditions. The PHORCYS system may be deployeddirectly into aquatic and marine environments, operate underwater, andincubate fluidic samples in situ. The system, in various embodiments,makes use of the classical approach of tracking dissolved speciesinvolved in photosynthesis and respiration (i.e., oxygen, nitrate,carbon dioxide, pH, etc.) over an incubation period. Various embodimentsmay share four basic elements: 1) an optically clear and/or opaqueincubation container/chamber that collects water; 2) a system to openand close the incubation container(s), thereby initiating andterminating the incubation period(s); 3) oxygen, nitrate, carbon dioxideor pH sensors, and/or variants thereof (including for concentration);and 4) an electronics unit/control module, which may provide power,record data, and/or transmit data. Still other embodiments of thePHORCYS instruments include apparatus to add substances such assolutions and/or particles to determine their impact on respiration orprimary production. Other embodiments include devices to take watersamples during the course of incubation, and automated valves foropening, rinsing and closing the incubation chambers. Some embodimentsmay depend on external rigging to position the PHORCYS instrument in theappropriate location of the water column and proper orientation tocollect and incubate samples under in situ conditions, such as adrifting array, anchored mooring, or lowering it from a pier or shipinto the water. Other embodiments may be self-ballasting andself-orienting, and may be part of a networked ocean observatory systemor incorporated into autonomous underwater vehicles and permanentlyreside in the ocean. Communications systems to transmit data to and/orreceive data from a remote location are also contemplated and consideredwithin the scope of the invention.

One embodiment of an aquatic sample analysis system 100 may be seen inFIG. 1. The system 100 includes an incubation chamber 102 a with asubstantially optically clear (i.e., transparent, translucent; allowsfor passage of ambient light) portion 103 a (the clear chamber) and anincubation chamber 102 b with a substantially optically opaque (i.e.,blocks ambient light) portion 103 b (the dark chamber), each of whichcontains a sensor, such as an oxygen optode (as described in greaterdetail below). The incubation chambers 102 a, 102 b may be generallycylindrical and are mounted to a common frame 104 with a control modulehousing 106 that houses a control module in communication with one ormore sensors. The control module 106 also operates spring-loaded caps108 between an open position to allow water to enter the incubationchambers 102 a, 102 b (and similarly to allow any water already presentto leave) and a closed position to enclose water (e.g., obtain a fluidicsample) in the incubation chambers 102 a, 102 b to initiate incubation.In certain embodiments, the chambers 102 a, 102 b may be sealed withhinged caps or some other closure mechanism or seal (e.g., ball valves).FIG. 1 depicts the chambers 102 a, 102 b having openings at both ends,though it is possible there is only one opening to the chamber 102 a,102 b (and the opening does not necessarily have to be at one endthereof). The system 100 also includes a power source disposed in thecontrol module housing 106. The components of the system 100 allow awater (freshwater or saltwater) sample to be enclosed, incubated insitu, and monitored for changes in oxygen concentration at a depth ofinterest. In some embodiments, only a single incubation chamber (e.g.,incubation chamber 102 a) may be used. In variations having only oneopen end, only one closure may be necessary to seal a chamber opening.

Another embodiment of an incubation chamber 202 for use with the system100 (either in addition to, or instead of, at least one of theincubation chambers 102 a, 102 b) is depicted in FIG. 2. The incubationchamber 202 has at least one ball valve 210 (there may be more than one,such as dual ball valves) to seal the incubation chamber 202. The ballvalve 210 may be only on one side of a semi-transparent portion 203 a ofthe incubation chamber 202, thereby allowing water in and out on oneside of the semi-transparent portion 203 a. Sensors 212, such as thosedescribed above, including an oxygen optode, may be located opposite theball valve 210 on the opposite end of the semi-transparent portion 203a. A separate control module housing 206 containing a control module tocontrol the ball valve 210 and/or the sensors 212 is also locatedopposite the ball valve 210. In certain embodiments, the ball valve(s)210 may be configured to repeatedly open and close the incubationchamber 202. Two or more semi-transparent portions 203 a may be used,particularly when the chamber 202 is intended to be deployed in darkambient settings where replicate respiration measurements are made. Thechamber 202 can be attached to other devices, such as sediment traps, inorder to enhance particle concentrations within the chambers.

FIG. 3A depicts an oxygen optode 314 for use with an aquatic sampleanalysis system, and may be particularly adapted to be disposed in achamber as described above (also in a chamber 302 with opaque walls asdepicted in FIG. 3B). The oxygen optode 314 may contain optical sensorsthat utilize a fluorescent platinum porphyrin complex embedded in a gaspermeable foil that is exposed to the surrounding water. Thefluorescence phase of the foil is proportional to the concentration ofoxygen in the surrounding water. This sensing foil is attached to awindow in a watertight titanium housing that contains the opticalinstruments. Through the window, the foil is excited by modulated bluelight and the phase of a returned red fluorescent light is measuredusing a photodiode. These sensors are designed to work under in situpressures and temperatures. Unlike O₂ electrodes, optodes do not consumeoxygen and are thus advantageous for measuring changes in oxygenconcentration in confined vessels, such as the incubators.

Some oxygen optodes, such as the Aanderaa oxygen optode (Aanderaa DataInstruments, Inc., Attleboro, Mass.) can measure oxygen with highresolution and accuracy and allow the PHORCYS system to measurerespiration rates as low as about 1 μmol O₂ L⁻¹ d⁻¹. In it presentembodiments, the sensitivity of the PHORCYS system is limited only bythe stability, accuracy and precision of the sensors, such as the oxygenoptode, that are contained with in it. This sensitivity, which issimilar to and may exceed the resolution of the Winkler titration method(comparative results using both methods are shown in Table 1), supportseffective determination of respiration rates in most aquatic waters withoxygen optodes. Moreover, whereas the Winkler method relies on solely afew measurements to establish rate-of-change of O₂ concentration,thousands of respiration rate measurements may be made with optode-basedrespirometers, providing greatly improved confidence in measured dataresults. Such systems, according to the invention, may be deployedeffectively in various applications, such as on wired ocean observingnetworks or autonomous profilers/gliders.

TABLE 1 Standard BOD with Winkler: 5.04 ± 0.12 μmol O₂ L⁻¹ d⁻¹ PHORCYS:2.770 ± 0.249 μmol O₂ L⁻¹ d⁻¹ Standard BOD with Winkler: 7.89 ± 0.34μmol O₂ L⁻¹ d⁻¹ PHORCYS: 8.100 ± 0.340 μmol O₂ L⁻¹ d⁻¹ Standard BOD withWinkler: 31.2 ± 2.3 μmol O₂ L⁻¹ d⁻¹ PHORCYS: 31.66 ± 0.49 μmol O₂ L⁻¹d⁻¹

The system 100 instruments collect data over time, such as oxygenconcentrations as detected by an optode-type oxygen sensor, as depictedin FIG. 4, though other data may be collected depending on the sensorsused, including nitrate concentration, carbon dioxide concentration, andpH. The dark/opaque incubation chamber 102 b records the decrease inoxygen due to respiration. Respiration is also observed in the clearincubation chamber 102 a during the night. Upon sunrise (approximately 6AM in the graph in FIG. 4) oxygen concentrations in the clear chamber102 a reflect the sum of gross respiration and gross primary production;this sum is also known as net primary production. In the above example,the gross respiration rate is 0.91±0.02 μmol O₂ hr⁻¹ and the net primaryproduction rate is 1.17±0.08 μmol O₂ hr⁻¹. Thus, the gross primaryproduction rate is 2.08±0.08 μmol O₂ hr⁻¹, as determined by thedifference between the gross respiration rate (negative slope) and thenet primary production rate (positive slope).

FIG. 5 depicts oxygen concentration results from additional testing,plotting results from the clear chamber 102 a, the dark chamber 102 b,and from shipboard incubations on the same graph. These results wereobtained when the system 100 was disposed at a depth of approximately 29m, at depth in the ocean that was effectively dark. The clear chamber102 a and the dark chamber 102 b provide continuous results throughoutthe testing, allowing a user to follow variations in results to identifyspecific times of interest, in contrast to the periodic observationsfrom shipboard incubations. Since the clear chamber 102 a and the opaquechamber 102 b remained in situ throughout the incubation, these resultswill be recognized by those skilled in the art as being more authenticrepresentations of natural respiration rates than the shipboardincubations. Further, as evidenced by the much smaller errors inrespiration rates, the continuous measurements in the clear chamber 102a and the dark chamber 102 b demonstrate greater sensitivity to changesin the fluidic sample than the results from the onboard incubations;this is particularly true of respiration rates based on the Winklermethod, which is mostly widely practiced by those skilled in the art.

The operational ranges of the system are generally dictated by thesensors. Presently, oxygen sensors, such as those from Aanderaamentioned above, are rated to 6,000 m depth (approximately 95% of all ofthe ocean is shallower than 6,000 m). The temperature range of thissensor is −5 to +40° C. However, the use of other sensors with greaterpressure handling capabilities and different temperature ranges iscontemplated, and considered within the scope of the invention.

Also, the incubation chambers may typically each have a volume betweenabout 1 and about 10 liters, though the chambers may be as small asabout 1 mL or less or as large as about 50 L (or more), depending on theapplication. In principle, the chambers may be configured to be anyshape or volume, and may be made of any functionally biologically inertmaterial, such as quartz or polytetrafluoroethylene.

In some embodiments, the system 100 is programmed before being deployed,e.g., by programming the control module. The programmable parameters mayinclude the times at which the chambers 102 a, 102 b close and open tocontrol the incubation period, the frequency of data collection by thesensors, power management, and mechanisms for data storage and/ortransmission. These parameters may also be controlled in real timethrough wired or wireless communications with the control module. Inother embodiments, the system's incubation chambers 102 a, 102 b closeautomatically, and then remain closed until the incubation period isover. For example, the spring-loaded lids 108 depicted in FIG. 1 maysnap shut on the chambers 102 a, 102 b after they are triggered by aburn wire once the system reaches a desired depth. Some embodiments ofthe system 100 can conduct multiple incubations by closing and openingthe chambers 102 a, 102 b repeatedly, and acquire, process, and transmitdata from multiple incubations. Some embodiments include injectionsystems to introduce other materials, such as particulate matter ordissolved chemicals, into the incubation chambers 102 a, 102 b, so thatthe impact of these other materials on respiration or primary productioncan be assessed.

Various embodiments and features of the present invention have beendescribed in detail with particularity. The utilities thereof can beappreciated by those skilled in the art. It should be emphasized thatthe above-described embodiments of the present invention merely describecertain examples implementing the invention, including the best mode, inorder to set forth a clear understanding of the principles of theinvention. Numerous changes, variations, and modifications can be madeto the embodiments described herein and the underlying concepts, withoutdeparting from the spirit and scope of the principles of the invention.All such variations and modifications are intended to be included withinthe scope of the present invention, as set forth herein. The scope ofthe present invention is to be defined by the claims, rather thanlimited by the forgoing description of various embodiments. Accordingly,what is desired to be secured by Letters Patent is the invention asdefined and differentiated in the claims, and all equivalents.

What is claimed is:
 1. An aquatic sample analysis system adapted for insitu use, the system comprising: an incubation chamber forming anopening for receiving a fluidic sample and adapted for use in the light;a seal for sealing the opening; an oxygen sensor capable of sensing anoxygen concentration associated with the sample inside the chamber inreal time; a control module in communication with the sensor and adaptedto determine a gross respiration rate during daylight without influenceof a production rate contribution and to repeatedly open and close theincubation chamber while in situ; and a power source.
 2. The system ofclaim 1, wherein the gross respiration rate is determined for awastewater management operation.
 3. The system of claim 1, wherein thechamber comprises a tube with at least one open end covered by the seal.4. The system of claim 3, wherein the at least one open end is sealableby a seal consisting of a spring-loaded cap.
 5. The system of claim 4,wherein the spring-loaded cap is biased toward a sealing position. 6.The system of claim 3, wherein the at least one open end is sealablewith a valve, wherein the valve is capable of automatically andrepeatedly opening and closing the incubation chamber when disposed. 7.The system of claim 3, wherein the at least one open end is sealablewith a hinged cap.
 8. The system of claim 1, further comprising anadditional sensor for sensing at least one parameter associated with thefluidic sample, wherein the at least one parameter is selected from thegroup consisting of a nitrate concentration, a carbon dioxideconcentration, and a pH.
 9. The system of claim 1, wherein the systemcomprises at least one sensor selected from the group consisting of aUV-based nitrate detector, a colorimetric carbon dioxide sensor, and acolorimetric pH sensor.
 10. The system of claim 1, wherein the controlmodule is adapted to provide power to the sensor and receive a sensoroutput.
 11. The system of claim 10, wherein the control module furtherstores the sensor output.
 12. The system of claim 1, wherein theincubation chamber is substantially optically opaque, the system furthercomprising a substantially optically clear incubation chamber.
 13. Thesystem of claim 12, wherein the substantially optically clear incubationchamber comprises a sensor for sensing at least one parameter associatedwith a sample inside the substantially optically clear incubationchamber.
 14. The system of claim 13, wherein the at least one parameteris selected from the group consisting of an oxygen concentration, anitrate concentration, a carbon dioxide concentration, and a pH.
 15. Thesystem of claim 13, wherein the control module is adapted to comparerespective outputs of the substantially optically clear incubationchamber sensor and the oxygen sensor.
 16. The system of claim 15,wherein the control module is adapted to determine at least one of aninstantaneous oxygen concentration, a gross respiration rate, a grossprimary production rate, and a net primary production rate.
 17. A methodof analyzing an aquatic parameter in situ comprising the steps of:deploying an aquatic sample analysis system to a location of interest;obtaining a fluidic sample within a first incubation chamber at thelocation of interest; measuring, in situ and without influence of aproduction rate contribution, an oxygen concentration associated withthe sample over an incubation period; calculating, without influence ofa production rate contribution, a gross respiration rate; and openingand closing repeatedly the first incubation chamber while in situ toobtain additional fluidic samples.
 18. The method of claim 17, whereinthe fluidic sample is sampled from wastewater management operation. 19.The method of claim 17, wherein the aquatic sample analysis systemfurther comprises a second incubation chamber comprising a substantiallyoptically clear portion.
 20. The method of claim 19, wherein a portionof the fluidic sample is disposed in each of the first incubationchamber and the second incubation chamber.
 21. The method of claim 19,wherein the calculating step comprises: calculating the grossrespiration rate based at least in part on a rate-of-change of oxygenconcentration in the first incubation chamber; calculating a net primaryproduction rate based at least in part on a rate-of-change of oxygenconcentration in the second incubation chamber; and determining thegross primary production rate based thereon.
 22. The method of claim 17,further capably comprising: releasing the fluidic sample repeatedly; andobtaining a new fluidic sample repeatedly.
 23. The method of claim 17,further comprising the step of adjusting incubation conditions, whereinthe incubation conditions comprise at least one of sensor parameters andincubation times.